Punnett Square

Homozygous

"Purebred" having two identical alleles for a trait Ex) BB

Codominance

A condition in which both alleles for a gene are fully expressed

incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.

Recessive

A trait that his hidden by a dominant trait. Need two traits for it to be expressed. (ex. bb)

dihybrid cross

Cross or mating between organisms involving two pairs of contrasting traits

Genotype

Letters expressing the types of genes.

The probability is 50%

One cat carries heterozygous, short-haired traits, and its mate carries homozygous long-haired traits. Use a Punnett square to determine the probability of one of their offspring having short hair.

Allele

One gene from a pair Ex) T or t

physical appearance

Phenotype refers to the ______________________ of an individual.

The probability is 100%

Red flowers are dominant to white flowers. A homozygous red flower is crossed with a homozygous white flower. Use a Punnett square to determine the probability of one of their offspring having red color.

The probability is 0%

Red flowers are dominant to white flowers. A purebred red flower is crossed with a white flower. Use a Punnett square to determine the probability of one of their offspring having a white color.

What do Punnett Squares show?

They show the probability of offspring inheriting particular genetic combinations.

Heterozygous

Two different alleles for a trait. "scientific name" Ex) Bb

The probability is 25%

Two heterozygous red flowers are crossed. Use a Punnett square to determine the probability of one of their offspring having a white color.

probability

a number that describes how likely it its that an event will occur

Dominant

a trait that is always expressed. It prevents a recessive from being expressed.

Phenotype

an organisms physical appearance of the gene Ex. tall, brown eyes, etc

meiosis

chromosome pairs separate and are distributed into new sex cells.

Genes

factors that control traits

XX

female sex chromosomes

XY

male sex chromosomes

Crossing over occurs during ______ to cause _____

meiosis; genetic variation

Hybrid

scientists call an organism that has two different alleles for a trait

test cross

the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype

sex-linked crosses

traits are carried on the sex chromosomes; notated with X and Y with traits as superscripts: no allele shown on Y chromosome

Punnett Square

used to determine all the possible outcomes of genetic cross

Purebred

when the alleles are the same (BB or bb) "common name"